Hello: I have a Yanmar 3GM in my Morgan 32. I changed out the raw water pump impeller and reinstalled the pump. Engine runs, can't get water out the exhaust port. I pulled the hoses so I know that the pump is at least not running dry. Anyone had this experience. Seems like a simple thing but it sure has me frustrated. Any advice would be appreciated. Kevin
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Have you let...
...the engine run enough to fill the heat exchanger and pump out raw water? The overheat signal may come on, but will still allow enough time that won't allow damage to occur to the engine.
...the engine run enough to fill the heat exchanger and pump out raw water? The overheat signal may come on, but will still allow enough time that won't allow damage to occur to the engine.
seal on strainer
I just had a problem with a 3GM on my YC's launch. Impeller burned out after overheating due to no water flow. Changed the impeller but still no water. Checked all hoses, fittings, etc....nothing. It ended up beaing the gasket on the raw water strainer (made for cork) was shot and was sucking air.
I just had a problem with a 3GM on my YC's launch. Impeller burned out after overheating due to no water flow. Changed the impeller but still no water. Checked all hoses, fittings, etc....nothing. It ended up beaing the gasket on the raw water strainer (made for cork) was shot and was sucking air.
Water
I am sure you checked the hose from the thru hull intake sea water, you opened the thru hull and checked to see if sea water is coming into pump. If you have water coming in and it should water come in as soon as you open the tru hull,open the thru hull to allow water into the strainer and loosen the strainer cap to allow some water and air to escape and do this as soon as you start the engine. Also could check to make sure the impeller is the correct one and is turning inside the pump,recheck everything you have done. Nick
I am sure you checked the hose from the thru hull intake sea water, you opened the thru hull and checked to see if sea water is coming into pump. If you have water coming in and it should water come in as soon as you open the tru hull,open the thru hull to allow water into the strainer and loosen the strainer cap to allow some water and air to escape and do this as soon as you start the engine. Also could check to make sure the impeller is the correct one and is turning inside the pump,recheck everything you have done. Nick
Boy, any number of things could be the cause
I had a friend who had a small fish sucked into the intake. He had water in the hose too, but not enough for cooling. You know its not coming out the exhaust, but do you have any volume at the mixing elbow? Do you have volume at the discharge side of the pump? Is the pump sucking? These things can all be checked with a bucket, or a bucket with water by disconnecting hose at various places to isolate the problem area. If its in the pump look at the impeller again. Impellers have been known to separate from the drive bushing. You might even have a broken piece of impeller in the pump discharge hose. I don't recall off hand if your pump is belt driven, could the belt be slipping? I think I would look at the discharge side of the pump first. It should be putting out a good stream of water, and you wouldn't have to run your engine more than a few seconds to know. Anyway, I think you have some more troubleshooting to do to isolate the problem. It could be a seal as Mike suggested but you have to look a little more.
I had a friend who had a small fish sucked into the intake. He had water in the hose too, but not enough for cooling. You know its not coming out the exhaust, but do you have any volume at the mixing elbow? Do you have volume at the discharge side of the pump? Is the pump sucking? These things can all be checked with a bucket, or a bucket with water by disconnecting hose at various places to isolate the problem area. If its in the pump look at the impeller again. Impellers have been known to separate from the drive bushing. You might even have a broken piece of impeller in the pump discharge hose. I don't recall off hand if your pump is belt driven, could the belt be slipping? I think I would look at the discharge side of the pump first. It should be putting out a good stream of water, and you wouldn't have to run your engine more than a few seconds to know. Anyway, I think you have some more troubleshooting to do to isolate the problem. It could be a seal as Mike suggested but you have to look a little more.
Yep, real easy to check through to the discharge side.
I popped a hose on that side Saturday. Nothing like a sharp knife for a quick fix.
I popped a hose on that side Saturday. Nothing like a sharp knife for a quick fix.
OK Sherlock
A. Did it work BEFORE you replaced the impeller? (assuming you did nothing else to change anything, then see "C") B. Did you replace the gasket with one of similar thickness? C. Did you prime the intake hose before starting it? D. There is no way you closed the thru hull valve and didn't open it (only powerboaters do this...so if you did, don't admit it!) My initial take on it would be you did not prime the hose. If you removed the cover from the impeller, you lost all the water from the intake hose, and the impeller won't be able to suck up enough to make water come thru the system. And you probably only have 2 gallons going thru the system at any one time.
A. Did it work BEFORE you replaced the impeller? (assuming you did nothing else to change anything, then see "C") B. Did you replace the gasket with one of similar thickness? C. Did you prime the intake hose before starting it? D. There is no way you closed the thru hull valve and didn't open it (only powerboaters do this...so if you did, don't admit it!) My initial take on it would be you did not prime the hose. If you removed the cover from the impeller, you lost all the water from the intake hose, and the impeller won't be able to suck up enough to make water come thru the system. And you probably only have 2 gallons going thru the system at any one time.
One trick we used recently to clear
any potential blockage at the thru hull: take the intake line off the pump and use a dinghy foot pump to blow through that line with the thru hull open. Worked for us.
any potential blockage at the thru hull: take the intake line off the pump and use a dinghy foot pump to blow through that line with the thru hull open. Worked for us.
priming a vane or diaphram pump
such as a raw water pump isn't necessary - they are self-priming (unless something else is wrong).
such as a raw water pump isn't necessary - they are self-priming (unless something else is wrong).
Is the impeller in right?
It is quite easy to put the impeller in backward. This results in some water flowing but not much. The path the water takes is input port, the long way around the pump impeller, output port. The pump does not "pump straight through" like you would think. Check the rotation and the impeller "fins" should be "following behind their hub". you only need to take off the back to see if you got them in backward.
It is quite easy to put the impeller in backward. This results in some water flowing but not much. The path the water takes is input port, the long way around the pump impeller, output port. The pump does not "pump straight through" like you would think. Check the rotation and the impeller "fins" should be "following behind their hub". you only need to take off the back to see if you got them in backward.
Maybe thermostat?
What's the engine temp. My universal doesn't start discharging water outboard until the thermostat reaches 140 degrees. Until then it recirculates the same water through the engine until running temperature is reached. Check the water hose after it's been running a few minutes the hoses should be getting warm meaning water is recirculating through the engine. If they are still cold then there is not circulation at all stop the engine and chech for obstructions. At some point the thermostat should open and discharge the hot water and refresh with new intake water.
What's the engine temp. My universal doesn't start discharging water outboard until the thermostat reaches 140 degrees. Until then it recirculates the same water through the engine until running temperature is reached. Check the water hose after it's been running a few minutes the hoses should be getting warm meaning water is recirculating through the engine. If they are still cold then there is not circulation at all stop the engine and chech for obstructions. At some point the thermostat should open and discharge the hot water and refresh with new intake water.
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